U.S. patent number 4,072,706 [Application Number 05/645,988] was granted by the patent office on 1978-02-07 for oxidation of phosphonomethylamines.
This patent grant is currently assigned to Monsanto Company. Invention is credited to James W. Gambell, Arnold Hershman.
United States Patent |
4,072,706 |
Hershman , et al. |
February 7, 1978 |
Oxidation of phosphonomethylamines
Abstract
Tertiary phosphonomethylamines are oxidized with oxygen,
preferably in contact with activated carbon, to cause cleavage of a
phosphonomethyl group and selective production of a secondary
amine.
Inventors: |
Hershman; Arnold (Creve Coeur,
MO), Gambell; James W. (St. Louis, MO) |
Assignee: |
Monsanto Company (St. Louis,
MO)
|
Family
ID: |
24591280 |
Appl.
No.: |
05/645,988 |
Filed: |
January 2, 1976 |
Current U.S.
Class: |
562/12; 562/16;
564/394; 564/468; 987/146; 987/217 |
Current CPC
Class: |
C07F
9/141 (20130101); C07F 9/3817 (20130101) |
Current International
Class: |
C07F
9/00 (20060101); C07F 9/141 (20060101); C07F
9/38 (20060101); C07F 009/38 (); C07C 085/20 () |
Field of
Search: |
;260/502.5,577,583R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Evans; Joseph E.
Attorney, Agent or Firm: Kennedy; Joseph D. Upham; John
D.
Claims
What is claimed is:
1. A process for production of secondary amines having at least one
phosphonomethyl group attached to the amine nitrogen which
comprises contacting a tertiary amine having more than one
phosphonomethyl group attached to the amine nitrogen and in which
other substituents on the nitrogen atom are not more readily
removable by oxidation than the phosphonomethyl group, with oxygen
at a temperature from ambient to about 250.degree. C and sufficient
to oxidize chemically the amine and effect removal of a
phosphonomethyl group, and recovering the resulting secondary amine
in substantial yield.
2. The process of claim 1 in which an activated carbon catalyst is
employed.
3. The process of claim 1 wherein pressure above atmospheric is
employed and temperatures in the range of about 75.degree. C to
about 150.degree. C.
4. The process of claim 2 wherein the tertiary amine is an
N,N,N-triphosphonomethyl amine.
5. The process of claim 2 wherein groups substituted on the
nitrogen of the tertiary amine are individually selected from
alkyl, aryl and phosphonomethyl.
6. The process of claim 1 in which an alkylene
bis-(iminodimethylenediphosphonic acid) is converted to an alkylene
bis (aminomethylenephosphonic acid).
7. The process of claim 1 in which the oxidation is conducted at
temperatures in the range of about 75.degree. C to 150.degree. C
employing a molecular oxygen containing gas, activated carbon
catalyst, and a solvent.
8. The process of claim 7 in which an aqueous reaction medium is
employed and actively effectively contacted with the oxygen
containing gas.
9. The process of claim 7 in which the partial oxygen pressure is
in the range of about 2 Kg/cm.sup.2 to about 7 Kg/cm.sup.2.
10. The process of claim 7 in which the secondary amine is
recovered in better than 80% yield.
11. The process of claim 2 in which the catalyst consists
essentially of activated carbon.
12. The process of claim 2 in which the catalyst comprises
activated carbon and noble metal.
13. The process of claim 1 in which a noble metal oxidation
catalyst is employed.
14. The process of claim 1 in which the process is conducted at
oxygen partial pressure of about 0.1 kg/cm.sup.2 to about 100
kg/cm.sup.2 with activated carbon catalyst.
15. A process for production of secondary amines which comprises
contacting an N-phosphonomethyl tertiary amine in which other
substituents on the nitrogen atom are not more readily removable by
oxidation than the phosphonomethyl group, said tertiary amine being
further defined as an N,N-dihydrocarbylaminomethylenephosphonic
acid, with oxygen employing an activated carbon catalyst at
temperatures from ambient to 250.degree. C and sufficient to
oxidize chemically the amine and effect removal of a
phosphonomethyl group, and recovering the resulting
N,N-dihydrocarbylamine in substantial yield.
Description
The present invention relates to a process for oxidative removal of
phosphonomethyl groups from tertiary amines. More particularly, the
present invention is concerned with such oxidation employing a
molecular oxygen-containing gas, preferably with an activated
carbon catalyst.
BACKGROUND OF THE INVENTION
It is known that certain tertiary amines can be converted to
secondary amines, and secondary amines to primary amines, by
electrochemical oxidation of amines containing phosphonomethyl
groups, as described in U.S. Pat. No. 3,907,652 to John H.
Wagenknecht and Kurt Moedritzer. A copending application of
applicant Arnold Hershman, Ser. No. 465,976, filed May 1, 1974, and
granted as U.S. Pat. No. 3,969,398 concerns a process employing
molecular oxygen-containing gas and activated carbon catalyst to
remove an acetic acid group from N-(phosphonomethyl) iminodiacetic
acid.
SUMMARY OF THE PRESENT INVENTION
The present invention concerns a process in which oxygen is
employed to oxidize a tertiary amine containing an
N-phosphonomethyl group to convert the tertiary amine to a
secondary amine in which a phosphonomethyl group has been replaced
by a hydrogen atom. The phosphonomethyl group has been found to be
readily and selectively removable under mild conditions in such
procedure from tertiary amines in which a phosphonomethyl group is
approximately as or more readily removable than other substituents
on the amine nitrogen. The selectivity of phosphonomethyl group
removal is particularly good when other substituents on the
nitrogen atom are relatively stable against oxidative removal
compared to the phosphonomethyl group, i.e. not removable under the
usual oxidation conditions or removable only at much slower rates.
In general it has been found that only one nitrogen substituent is
removed, so that the removal of the phosphonomethyl group produces
the corresponding secondary amine, thereby providing a convenient
and selective synthesis of such secondary amines.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to the oxidative removal of
phosphonomethyl groups from amine nitrogen. The invention involves
the chemical oxidation of tertiary amines containing an ##STR1##
function, in which the R's are individually selected from hydrogen,
or salt or ester forming groups. The reaction results in removal of
the phosphonomethyl group and its replacement by a hydrogen
substituent on the amine nitrogen. The reaction is employed to
selectively convert tertiary amines to secondary amines.
The reaction can be illustrated: ##STR2## where R' and R" are
individually selected from organo substituents not more readily
removable by oxidation than phosphonomethyl, or together form part
of a ring compound, and R is individually selected from hydrogen or
salt or ester forming groups. The reaction thus produces a
secondary amine corresponding to the starting phosphonomethyl
amine, but from which a phosphonomethyl group has been removed. The
other products in most cases in aqueous solution are phosphorous
acid or derivative and formic acid.
In the above illustrated reaction either or both of R' and R" can
and often are phosphonomethyl groups, or monovalent hydrocarbyl
groups, or such groups with imino, amine, including dialkyl or
other substituted amine, or halo, oxygen or sulfur
substituents.
The illustrated reaction employs tertiary phosphonomethylamines,
and such tertiary amines are often reagents available for
modification and which may be desired in the form of secondary
amines. At times secondary amines are difficult to prepare by usual
procedures without contamination by primary and tertiary amines. In
the present process it has been found feasible to selectively
oxidize to the secondary amine.
The phosphonomethyl amines which are oxidized in the present
process can and often do contain more than one N-phosphonomethyl
group, as exemplified for example by the reaction of
nitrilotrimethylenetriphosphonic acid:
in previously employed procedures, generally an amine or ammonia,
formaldehyde, and orthophosphorous acid react to form the fully
substituted amine, and attempts to prepare secondary amines by this
reaction generally lead to a mixture that is very difficult to
separate. This has resulted in use of a modified, multi-step
process to prepare amines such as iminodimethylenediphosphonic
acid, HN (CH.sub.2 PO.sub.3 H.sub.2).sub.2. The present invention
provides the second step of a two-step synthesis of, for example,
iminodimethylenediphosphonic acid by oxidation of a tertiary amine
obtained from reaction of ammonia, formaldehyde and
orthophosphorous acid.
The phosphonomethyl compounds used as reactants herein can have the
phosphono moiety in the phosphonic acid form, or in the form of
various derivatives thereof such as salts and esters. Thus in the
--CH.sub.2 PO.sub.3 R.sub.2 moiety the R groups can, for example,
individually be hydrogen, alkali metal, alkaline earth metal, iron,
nickel or other transition metals, ammonium and organoammonium,
monovalent hydrocarbon radicals containing 1 to 12 carbon atoms,
halogenated monovalent hydrocarbon radicals hydrocarbon
oxyhydrocarbon groups containing 1 to 4 carbon atoms
interconnecting the hydrocarbon moieties.
Illustrative of the monovalent hydrocarbon radicals represented by
R are alkyl groups of the formula C.sub.a H.sub.2a+1, such as
methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl and
their isomers, etc.; alkenyl groups of the formula C.sub.a
H.sub.2a-1, such as ethenyl, propenyl, butenyl, octenyl, dodecenyl
and their isomers, etc.; aryl groups containing 6 through 10 carbon
atoms such as phenyl, tolyl, xylyl, ethylphenyl, diethylphenyl and
the like; aralkyl groups such as benzyl, phenylethyl, phenylpropyl,
dimethylphenylpropyl, dimethylphenylbutyl and the like; and the
halogenated derivatives thereof containing up to 3 halogen
atoms.
By the term halogen as employed herein is meant fluorine, chlorine,
bromine and iodine.
The term "alkali metal" encompasses lithium, sodium, potassium,
cesium, and rubidium; and the term "alkaline earth metal" includes
beryllium, magnesium, calcium, strontium and barium.
The phosphonomethyl moiety in any of the illustrative reactions
herein can have R groups in accordance with the foregoing
disclosure. The phosphonomethyl group containing compounds will in
general be employed in the same way in the reaction, aside from the
type of phosphonic acid derivative employed, except for the ester
or other derivative groups having some effect upon solubility of
the reactant in the reaction medium. In general high solubility is
not necessary for the oxidation, but some solvents are particularly
suited to organic soluble esters. The isolation procedures may also
vary with the particular derivative and the form in which it is to
be isolated.
The present invention may be most useful in the modification of
amino phosphonoate compounds known to be useful and used as
sequestering agents for metal ions or used as threshold agents to
inhibit precipitation and scale formation.
A particular type of compound for which the present invention will
be useful in removing phosphonomethyl groups is represented by the
formula:
and the reaction results in the removal of one phosphonomethyl
group, represented by A, to produce ##STR3## with possibly
additional changes in the G moiety, depending upon whether it
contains additional phosphonomethyl groups subject to removal. In
the above formula, A represents a phosphonomethyl group, --CH.sub.2
--PO.sub.3 R.sub.2 in which R has the same meaning as hereinbefore,
and G is selected from A, alkyl, especially lower alkyl, aralkyl,
cycloalkyl, hydroxyalkyl and [--(CH.sub.2).sub.n --(B).sub.m
--].sub.p (CH.sub.2).sub.n --N(A).sub.2 in which B is ##STR4##
where Z is A, lower alkyl, aralkyl, or cycloalkyl, and m is 0 or 1,
n is an integer from 1 to 12, preferably from 1 to 6, p is an
integer from 1 to about 2000 or more. It will be apparent that the
above formula includes, for example, such variations in the
reactant as illustrated by the following: ##STR5## in which the
symbols have the same meaning as described above, and all of these
types of compounds can be utilized in the present process. The
alkylene linkages in these reactants are ordinarily saturated, or
at least ordinarily contain no non-aromatic unsaturation, but there
is no fundamental reason why olefinic or other unsaturated groups
should not be present, except certain olefinic structures may
cleave rather than A. Various other types of groups can also be
present, but if such groups are readily oxidized, the resulting
product may be modified by the oxidation of that group, as well as
by removal of the phosphonomethyl group, and the significance of
this will depend upon the particular reactant and the desired
product. The methyl group of the phosphonomethyl group ordinarily
bears no substituent other than the phosphono group, but can have
non-interfering substituents, such as in
nitrilotri-(ethylidenephosphonic acid) and other phosphonomethyl
amines in which the methyl group has a lower alkyl substituent and
one free hydrogen. The phosphonomethyl groups can also, for
example, appropriately be attached to the nitrogen
polyethyleneimine resins as reactants.
The present process involves reactions of tertiary amines to obtain
secondary amines, and the secondary amines are in general resistant
to further cleavage reactions. The N-phosphonomethyl groups can be
removed from tertiary amines containing various other groups, for
example, such groups as --CH.sub.2 CH.sub.2 OH, --CH.sub.2 CH.sub.3
--C.sub.6 H.sub.5, --CH.sub.2 CH.sub.2 COOH, --CH.sub.2 C.sub.6
H.sub.5, etc., and various other groups in the illustrative
reactants described herein. The illustrative reactants exemplify
some types of reactants which may be of particular interest for use
in the present process. However the process is applicable to broad
classes of tertiary amines containing N-phosphonomethyl groups, for
example such amines in which theother substituents are alkyl
groups, or aryl groups, or various hydrocarbyl groups. In general
such substituents can suitably be present regardless of size or
number of carbon atoms, but ordinarily will be in available ranges
of 1 to 20 or so carbon atoms and lower alkyl or lower aryl groups
may often be most convenient for use.
Phosphonomethylamines of the type utilized as reactants herein are
known agents for various water treating and similar purposes,
particularly as scale inhibiting agents as described in U.S. Pat.
No. 3,336,221, and as metal ion sequestering agents as described in
U.S. Pat. No. 3,234,124, and the compounds described in these
patents can in general be employed in the present process. In
addition, the compounds resulting from the present process will in
general be suitable for the same purposes, although possibly in
greater or lesser degree, especially when the resulting compound
still includes one or more of the phosphonomethyl groups. In
addition to scale inhibition in boiler waters etc., such agents are
effective in inhibiting corrosion of iron, steel and other metal
coming into contact with such water under highly oxygenated or
otherwise possibly corrosive conditions. Because of their
inhibiting, anti-precipitant, chelating and sequestering
properties, such agents are usefully employed in various soaps,
detergents and cleaning compounds, and the products of the present
process can be employed in the same applications. In addition some
of the products of the present process are known compounds of known
utility in such applications. A number of the reactants utilized in
the present process are sold under the Dequest trademark for scale
inhibition, sequestering metal ions, etc. The products of the
present process may have advantages in greater or easier
biodegradability.
The present process is effected by contacting the N-phosphonomethyl
tertiary amine with oxygen, preferably in the presence of an
oxidation catalyst. Preferred temperatures are in the range of
about 75.degree. C to about 150.degree. C, but lower or higher
temperatures can be used, such as from ambient temperatures to
about 250.degree. C or higher. The temperature affects the reaction
rate with indications that, over preferred ranges, about a
15.degree. C. increase can be expected to cause a doubling of the
reaction rate. The reaction rate also increased with increasing
oxygen concentration. It appears that one-half an oxygen molecule
is utilized for each phosphonomethyl group cleaved. In practice,
the amount of oxygen reacted will be from 1/2 to 1 or more moles
oxygen for each N-phosphonomethyl group cleaved. Mild conditions of
temperature and pressure are suitable for the reaction and can
conveniently be employed, but higher pressures are also suitable,
for example, oxygen partial pressures from about 0.1 Kg/cm.sup.2 to
100 or more Kg/cm.sup.2. The total pressure in the reaction system
will ordinarily be in the range from about ambient atmospheric
pressured up to 200 Kg/cm.sup.2 or higher, and oxygen can be
supplied as such or in molecular oxygen-containing gas. It has been
found that oxygen partial pressures of from about 2 Kg/cm.sup.2 to
about 7 Kg/cm.sup.2 can be conveniently employed and ordinarily
give suitable reaction rates. Temperatures employed should be
sufficient to initiate the reaction and to sustain the reaction
once initiated, and temperatures sufficient to give desirable
reaction rates will depend upon the catalyst and other reaction
conditions, and upon the particular N-phosphonomethylamine
reactant.
The manner in which the N-phosphonomethylamine is contacted with
the molecular oxygen-containing gas and preferably activated carbon
or other catalyst can vary greatly. For example, the amine can be
placed in a closed container with some free space containing
molecular oxygen and shaken vigorously or agitated by stirring, or
the molecular oxygen-containing gas can be bubbled through a
solution of amine containing activated carbon, either through a
straight tube or a tube with a fritted diffuser attached thereto.
The contacting can also be accomplished in a tubular continuous
reactor packed with activated carbon. Thus, the process of this
invention can involve actively contacting effectively the molecular
oxygen-containing gas with an aqueous solution of N-phosphonomethyl
amine containing activated carbon catalyst as illustrated
hereinabove. As those skilled in the art would realize, merely
allowing a water solution of said amine containing said activated
carbon to stand in contact with air under proper conditions would
produce some of the desired product; however, the amount so
produced would be small.
In conducting the process of this invention it is preferred to
employ approximately saturated solutions of the N-phosphonomethyl
amine in water at the temperature of reaction for ease of reaction
and ease of recovery of the product. It is, of course, possible to
employ very dilute, i.e. 0.1% by weight of N-phosphonomethyl amine
in water; however, this results in a more difficult product
recovery procedure. It is also possible to employ supersaturated
solutions; however, the use of such solutions is usually not as
desirable since the starting material could precipitate out during
the reaction, thereby rendering the reaction process more difficult
to conduct and separation of the product more difficult.
The reaction rate is influenced to some extent by concentration of
the amine, but suitable results can be obtained over boad ranges,
and, moreover, at low conversions the concentration appears to have
little effect upon rate. However, at higher conversions, the rate
appears to decrease with decreasing concentration. The reaction can
be conducted in solvents, or can be conducted by contacting the
N-phosphonomethylamine with oxygen in the absence of solvent,
preferably under conditions in which the amine is in liquid form.
Water is a convenient and preferred solvent, but various other
solvents can be used, e.g. glacial acetic acid, aqueous acetic
acid, a mixture of acetic acid and acetic anhydride, etc., or
various other solvents which are resistant to oxidation under the
reaction conditions. Water is a suitable solvent, and ordinarily
there is no reason to utilize other solvents unless effective in
aiding solution of the amine reactant to facilitate the
oxidation.
It is advisble to have the amine reactant in solution or other
mobile, tractable form to facilitate the reaction. Some amines will
be in liquid form under the reaction conditions and will need no
solvent or similar component. While ordinarily the amine will be at
least partially soluble in the reaction medium, it is also possible
to conduct the reaction with a slurry, emulsion, or suspension of
the amine in liquid medium. Illustrative of other solvents or
liquids which can be employed are nitriles such as acetonitrile,
propionitrile, benzonitrile, etc.; nitro compounds such as
nitromethane, nitroethane, etc.; halogenated hydrocarbons such as
methylene chloride, ethylene chloride, carbon tetrachloride, etc.;
and dimethyl formamide and dimethyl sulfoxide.
The acid-base character of the reaction medium appears to have some
influence on the oxidation, but its effect on reaction rate varied
with particular amines and the extent of conversion. The reaction,
however, is operable over wide ranges of pH conditions, and there
is no requirement to regulate this parameter, although there may be
advantage on occasion in doing so. The pH of the reaction medium
may vary from the presence of the amine reactant and carbon over
ranges, for example, from 1 to 10 or so, and if desired acids such
as hydrochloric or phosphoric can be employed as reaction medium,
or bases such as sodium hydroxide. If desired, various salts or
other materials may be present in the reaction medium, although
ordinarily they will serve no useful purpose and may contribute to
side reactions. Surfactants, such as emulsifying agents and the
like, may possibly be used with advantage at times. Ordinarily for
commercial practice it will not be desirable to select materials
providing reactive halide or halogen, such as hydrochloric acid,
because of the possible corrosive effect upon equipment, but the
oxidation reaction is nevertheless operable in the presence of such
materials.
By the term "molecular oxygen-containing gas", as employed herein,
is meant any gaseous mixture containing molecular oxygen with one
or more diluents which are nonreactive with the oxygen or with the
reactant or product under the conditions of reaction. Examples of
such gases are air, oxygen, oxygen diluted with helium, argon,
nitrogen, or other inert gas, oxygen-hydrocarbon mixtures and the
like. It is preferred to employ gases containing 20 or more percent
by weight molecular oxygen and even more preferred to employ gases
containing 90 or more percent by weight molecular oxygen. It is, of
course, obvious to those of ordinary skill in the art that when
molecular oxygen-containing gases containing other inert gases are
employed, the pressures should be increased to maintain adequate
partial pressures of oxygen in the system to maintain a sufficient
rate of reaction.
The process of the present invention can be conducted in a reaction
vessel without any added catalyst and at appreciable rates, but
such rates with, for example, nitrilotrimethylenetriphosphonic
acid, are improved about 10-fold by activated carbon catalyst. It
is a particular aspect of the present invention to carry out the
present invention with a carbon catalyst. Any source or form of
carbon can be used as a catalyst or substrate in the process of the
present invention; for example powdered lampblack can be used and
appreciable reaction rates are obtainable. However, reaction rates
are markedly improved with activated carbons, which ordinarily have
much higher surface areas than non-activated carbons, e.g. 551
m.sup.2 /gram for a particular activated carbon employed, compared
to 21 m.sup.2 /gram for a non-activated powdered lampblack.
The activated carbon catalysts employed in the process of this
invention are well known in the art and are available under a large
number of trade names. These activated carbons are characterized by
high absorptive capacity for gases, vapors and colloidal solids and
relatively high specific surface areas. Carbon, char or charcoal is
produced by destructive distillation of wood, peat, lignite, nut
shells, bones, vegetable or other natural or synthetic carbonaceous
matter, but must usually be "activated" to develop adsorptive
power. Activation is usually achieved by heating to high
temperatures (800.degree.-900.degree. C.) with steam or with carbon
dioxide, which brings about a porous particle structure and
increased specific surface area. In some cases hygroscopic
substances, such as zinc chloride and/or phosphoric acid or sodium
sulfate, are added prior to the destructive distillation or
activation, to increase adsorptive capacity. The carbon content of
active carbons ranges from about 10% for bone charcoal to about 98%
for some wood chars and nearly 100% for activated carbons derived
from organic polymers. The non-carbonaceous matter in activated
charcoal will vary depending on precursor origin and/or activation
procedure. For example, inorganic " ash" components containing
aluminum and silicon are oftentimes present in large amounts
accompanied by certain alkali metals and alkaline earths. The
latter grouping influences, in part, the acidity-basicity
characteristics of the activated carbon. Other inorganic
constituents found in many activated carbons include iron and
titanium. Depending on raw material origin and activation
procedure, large amounts of oxygen can be present along with lesser
amounts of hydrogen, nitrogen and sulfur. Oxygen content also
influences activated carbon acidity-basicity.
The specific surface area of activated carbons, measured by the BET
(Brunauer-Emmett-Teller) method using N.sub.2, can range from 100
to nearly 2000 m.sup.2 /gram. The packed bulk density of activated
carbons will depend on the form (powder vs. particulate), porosity
and also on the measuring technique employed. Measured values less
than 0.15 g/cc and as high or about 0.6 g/cc for powders have been
recorded. Particle or skeletal density, determined by mercury
intrusion at atmospheric pressure, ranges from about 0.2 g/cc to
about 0.53 g/cc on the same samples. Of course, density values on
either side of the ranges are possible and it is understood that
the values cited are for illustrative purposes and should not be
construed as limiting the scope of the present invention.
The specific surface area of the activated carbon employed in the
process of this invention will generally be in the range of from
100 to 2000 square meters per gram. It is preferred to employ
activated carbons having a specific surface area of from 400 to
1600 square meters per gram.
The amount of granular or powdered activated carbon employed in the
process of this invention can vary widely, ranging for example from
0.5 to 100 or more parts by weight for every 100 parts by weight of
the N-phosphonomethyl amine employed. For the powdered activated
carbons, it is preferred to employ from 5 to 100 parts by weight of
activated carbon for each 100 parts by weight of the
N-phosphonomethyl amine. For the activated carbons in granular
forms, it is preferred to employ 10 to 200 parts by weight per 100
parts by weight of N-phosphonomethyl amine. It is, of course,
obvious that in a tubular type continuous reactor, weight ratios of
activated carbon to reactants can vary over even greater ranges
than herein set forth.
The activated carbons employed in the process of this invention can
be in the form of powders or granules, or various particulate forms
or shapes, or as coatings on various substrates or structures.
In the powder form the activated carbons consist largely of
material having a particle size finer than 325 mesh (about 45
microns or less in diameter)--although some larger particles may
also be present. Particles as small as one micron have been
observed by scanning electron microscopy. In the granular form, the
particle size range can vary considerably. Particle sizes of 4
.times. 10 mesh, 8 .times. 30 mesh and 20 .times. 30 mesh are all
available commercially and can be used. Mesh sizes given herein are
those of the U.S. Standard Sieve Series.
The following is a listing of some of the activated carbons which
are useful in the process of this invention. This listing is by way
of example and is not an exhaustive listing. These activated
carbons are for example:
______________________________________ Trade Name Sold by
______________________________________ Darco G-60 Spec. ICI-America
Wilmington, Delaware Darco X " Norit SG Extra Amer. Norit Co., Inc.
Jacksonville, Fla. Norit EN4 " Norit EXW " Norit A " Norit Ultra-C
" Norit ACX " XZ Barnebey-Cheney Columbus, Ohio NW " JV " Bl. Pulv.
Pittsburgh Activated Carbon Div. of Calgon Corporation Pittsburgh,
Pa. PWA Pulv. " PCB fines " P-100 No. Amer. Carbon, Inc. Columbus,
Ohio Nuchar CN Westvaco Corporation Carbon Department Covington,
Va. Nuchar C-1000N " Nuchar C-190A " Nuchar C-115A " Code 1551
Baker and Adamson Division of Allied RB-111 Amer. Norit Co., Inc.
Jacksonville, Fla. Norit 4 .times. 14 mesh " GI-9615
Barnebey-Cheney Columbus, Ohio VG-8408 " VG-8590 " NB-9377 " Grade
235 Witco Chemical Corp. Activated Carbon Div. New York, New York
Grade 337 " Grade 517 " Grade 256 " Columbia SXAC Union Carbide New
York, New York ______________________________________
The following table gives the properties of a number of common
activated carbons in powder form.
______________________________________ POWDERS
______________________________________ Specific Surface Pore Bulk
pH Area (BET Volume Density Water Trade Name m.sup.2 /g cc/g g/cc
Solution ______________________________________ Darco G-60 1144
2.819 .310 7.5 Darco X 296 1.555 .440 5.0 Norit SG Extra 820 1.669
.431 6.9 Norit EXW 1082 2.205 .350 6.6 Norit Ultra C 1076 2.206
.354 10.0 Norit A 900 .384 9.0 Norit ACX 1360 2.4 Norit EN4*
551-900 .401 7.0 YZ 1136 1.402 .561 8.4 NW 662 1.405 .482 11.4 JV
743 1.599 .498 2.8 Black-pulverized 972 1.600 .551 8.9
PWA-pulverized 898 1.641 .520 8.2 PCB-fines 1010 1.502 -- 10.01
P-100 1394 2.500 .383 2.5 Nuchar CN 963 4.537 .178 7.1 Nuchar
C-1000N 986 4.918 .147 6.2 Nuchar C-190A 796 4.211 .222 5.3 Nuchar
C-115A 815 3.877 .251 5.6 Code 1551 458 2.310 -- 3.4
______________________________________ Norit EN4* = Purchased from
Fisher Scientific Company, Fairlawn, New Jersey.
The following list gives properties of some granular activated
carbons.
______________________________________ Specific Surface Particle
Area Density Trade Name Mesh m.sup.2 /g pH g/cc
______________________________________ Norit RB 111 4 .times. 14
797 9.2 .655 Norit 4 .times. 14 mesh 4 .times. 14 615 10.5 .530 GI
9615 8 .times. 14 1723 11.2 .650 VG-8408 6 .times. 10 670 9.2 .837
NB-9377 4 .times. 10 610 10.5 .619 Grade 235 4 .times. 10 1046 9.8
.926 Grade 235 8 .times. 30 .918 Grade 337 8 .times. 16 Grade 337
10 .times. 20 Grade 517 8 .times. 30 Grade 517 18 .times. 40 Grade
256 4 .times. 10 1130 9.9 .788 Columbia SXAC 6 .times. 8 1245 7.1
.747 ______________________________________
The activated carbons used herein can be supported on other
substrates, inert or otherwise. For example, suitable results were
obtained with a carbon-on-alumina catalyst which was prepared by
decomposing a butene at a temperture of about 450.degree. C over a
5/8 mesh activated alumina, the carbonaceous layer being
substantially devoid of oxygenated compounds due to preparation in
inert atmosphere. The specific catalyst employed contained 30.47%
by weight carbon.
In place of, or in addition to, the carbon, various other oxidation
catalysts can be employed, particularly metallic catalysts such as
various noble or base metals or their oxides. Such catalysts will
ordinarily be utilized in known ways as dispersions or coatings on
or impregnates in various substrates. In view of the effectiveness
of carbon catalyst, there is generally no reason to employ metal or
other generally more expensive catalysts. However noble metals are
very effective oxidation catalysts for the reaction and can be
employed. On a weight per weight basis, noble metals tend to
produce more rapid reaction rates than activated carbon, and hence
there may at times be advantage in combining the noble metals, such
as rhodium or palladium, with activated carbon. Such metals are,
however, less readily available and more expensive, and therefore
customarily used in lower concentration in catalysts, in which form
they may be comparatively less effective than activated carbon.
Moreover, the noble metals tend to be leached out of carbon along
with amine reactants or product in isolation or other procedures
prior to recycling catalyst and other materials to a reactor, and
this tends to negate any advantage in use of such materials. The
noble metal catalysts for use herein can be prepared by various
impregnation, precipitation or reduction procedures. For example,
carbon can be added to a solution of chloroplatinic acid, and
sodium borohydride then slowly added, followed by dropwise addition
of hydrochloric acid to obtain a slightly acidic pH. The amine
reactant can then be added to the catalyst mixture. Other known
ways of impregnating noble metals on substrates, as by absorption
and decomposition of suitable salts often followed by reduction,
can be employed.
EXAMPLE 1
Oxidations were carried out in a stainless steel 300 ml. autoclave
reactor equipped with agitator and a bottom sampling valve. Reactor
temperature was measured with an internal thermocouple and
regulated with a temperature controller. The reactor could be
operated with oxygen continually flowing, or dead-headed, and both
procedures were demonstrated effective for oxidations described
herein. The oxygen feed was through a dip tube with holes drilled
in it for sparging. Pressure change in the reactor was measured
versus a set load cell pressure, and recorded. In dead-head
operation, the oxygen admission control valve was opened to admit
oxygen to the desired pressure, usually after obtaining desired
operating temperature, and the valve was then closed. The reactor
could then be repressured periodically by opening the control
valve. For continuous flow, reactor pressure was controlled by a
back pressure regulator on the exit line and an oxygen flow rate
controller and valve on the inlet. In the continuous flow
operation, the flow rate was generally 60 cc/minute (S.T.P.) of
oxygen. The reaction was monitored by oxygen uptake, and analysis
of off-gases, for carbon dioxide and by nuclear magnetic resonance
analysis of periodic or final product samples. There was fairly
good agreement with respect to the conversions shown by different
methods when several measurements were taken. Reactant and solvent
were charged to the reactor. Catalyst, if employed, was charged
separately, such as powdered activated carbon, which was then
employed in slurry form. The reactor was then brought to desired
temperature and oxygen pressure. The procedure was carried out with
N [CH.sub.2 PO(OH).sub.2 ].sub.3 as reactant, with 10 grams being
employed with 0.5 gram Norit "A" carbon, and 100 ml deionized
water, at 115.degree. C and 100 psi oxygen gauge pressure, using
dead-head operation. The product was the expected secondary amine,
NH[CH.sub.2 PO(OH).sub.2 ].sub.2, with 60% conversion in 50
minutes, and 95-99% in 140 minutes. There was no evidence of
primary amine formation even after 200 minutes. In a comparison run
with no carbon or other catalyst, a 30% conversion to the secondary
amine was obtained in 180 minutes. In place of the dead-head
operation, continuous oxygen flow can be utilized with similar
results, but continuous flow was usually used only when carbon
dioxide was expected as one of the primary cleavage products and
the oxygen flow would be useful in removing it from the reactor.
Similar results can be obtained with other phosphonomethylamines,
for example under the same reaction conditions substantial
conversions can be obtained of ethyliminodiphosphonic acid to
ethylaminophosphonic acid, and of N-ethyl-N-propylaminophosphonic
acid to ethylpropylamine. Also other catalysts can be employed with
good results, as other carbons listed herein, viz. Nuchar CN and
Darco X, and a carbon-on-alumina catalyst prepared by decomposition
of butene over an alumina catalyst. Similar results can also be
obtained with 5% by weight Rh on carbon, 5% by weight Rh on alumina
(KA-101) catalysts, or with other noble metals on carbon, alumina
or other catalyst supports, for example 5% by weight Pd on alumina,
or Pt or Ru or other noble metal oxidation catalysts.
EXAMPLE 2
Nitrilotrimethylenetriphosphonic acid was oxidized, employing 0.5
gram Norit "A" carbon and 100 ml water with 10 grams of the
reactant, and conditions and results as tabulated in Table 1. Good
conversions to the secondary amine, iminodimethylenediphosphonic
acid, were obtained over the temperature and pressure ranges
employed. In some instances two values are reported for the
reaction half-life, one early in the run and one from the best
correlation later in the run.
Table 1
__________________________________________________________________________
Oxidative Cleavage of N[CH.sub.2 PO(OH).sub.2 ].sub.3, "Dequest"
2001
__________________________________________________________________________
Temperature Pressure O.sub.2 Reaction Rate Cumulative Reaction Run
(.degree. C) (psi) t-1/2 (min) Time (min) % Conversion.sup.1,2
__________________________________________________________________________
A 95 30-35 120-90 420 95+ B 115 30-35 52-44 255 95-99 C 115 100
32-28 200.sup.4 100 D 130 35 45-30 240 100 E 95 100 42 210 95
F.sup.3 130 95 10 40 95 G.sup.3 95-115 95 <20 120 100 135 165
230.sup.4 100 H.sup.3 95 60 75 30 25 115 60 40 120 85 135 100 --
210.sup.4 100
__________________________________________________________________________
.sup.1 Product was NH[CH.sub.2 PO(OH).sub.2 ].sub.2 and cleavage
fragment were H.sub.3 PO.sub.3 and HCOOH. All were positively
identified by proton nmr. Conversion estimated from nmr peak areas.
.sup.2 A small quantity of an unidentified material appeared in the
nmr spectra of most of the samples. .sup.3 Six (6) gms of "Dequest"
2001 reactant. .sup.4 Continued run after tertiary amine converted
to secondary amine. However, no evidence of primary amine
formation.
EXAMPLE 3
Various phosphonomethyl amines were oxidized in the reactor and
employing the general procedure of Example 1, under conditions as
tabulated in Table 2. The desired secondary amines were obtained,
and often with good selectivity. Where conversions are incomplete,
improvement can generally be obtained by longer reaction times or
other procedures. It will be noted that the products still have
methylenephosphonic acid groups (designated by PM), and will be
useful for sequestering agents and similar purposes as described
herein.
Table 2
__________________________________________________________________________
Oxidative Cleavage of Phosphonomethylamines
__________________________________________________________________________
Conditions: 0.5-1.5 g Norit "A" activated carbon; 100-150 ml
H.sub.2 O solvent; 100 psi O.sub.2 pressure. Reaction Cleavage
Fragments Run Moles Temp Time % % No. Starting Amine (gms)
(.degree. C) (hrs.) Conv.sup.1 Amine Products.sup.2 CO.sub.2.sup.3
Others.sup.2
__________________________________________________________________________
I CH.sub.3 N(PM).sub.2 .033 115-135 4 55 CH.sub.3 NH(PM) <10
HCOOH, H.sub.3 PO.sub.3 (7.3) ##STR6## 0.15 (4.0) 115 3 100
##STR7## <10 HCOOH, H.sub.3 PO.sub.3 K CH.sub.2 CHCH.sub.2
N(PM).sub.2 .033 115-135 5 60 CH.sub.2 CHCH.sub.2 NH(PM).sup.4 3
HCOOH, H.sub.3 PO.sub.3 (8.0) L CH.sub.2 CHCH.sub.2 N(PM).sub.2
.021 115 6 80 CH.sub.2 CHCH.sub.2 NH(PM).sup.4 10 HCOOH, H.sub.3
PO.sub.3 (5.0) M .phi.CH.sub.2 N(PM).sub.2 .010 115 4 100
.phi.CH.sub.2 NH(PM).sup.4 /NH(PM).sub.2 8 25 HCOOH.sup.6 (3.0)
(molar ratio .about. 2.5/1) N [(PM).sub.2 NCH.sub.2].sub.2 .018
95-130 4 100 [(PM)NHCH.sub.2].sub.2,,.sup.4 HN(PM).sub.2 --
HCOOH,.sup.6 HCHO (4.0) and unidentified O [(PM).sub.2
NCH.sub.2].sub.2 .018 115 3 100 [(PM)NHCH.sub.2].sub.2,.sup.4
HN(PM).sub.2 -- HCOOH,.sup.6 HCHO (4.0) and unidentified P
[(PM).sub.2 N(CH.sub.2).sub.3].sub.2 .010 115 21/4 100 Product(s)
of PM cleavage --.sup.5 HCOOH.sup.6 (2.5) Q [(PM).sub.2 NCH.sub.2
CH.sub.2S].sub.2 .010 115 51/2 100 [(PM)NHCH.sub.2 CH.sub.2
].sub.2S.sup.4 10 HCOOH, H.sub.3 PO.sub.3 (2.5)
__________________________________________________________________________
.sup.1 Estimated conversion of the starting amine from proton nmr
peak areas. .sup.2 Unless otherwise noted, positively identified by
proton nmr. .sup.3 Mole % CO.sub.2 based on starting amine
(semi-quantitative). .sup.4 No reference compounds available. NMR
spectra are consistent with structures assigned. .sup.5
Considerable CO.sub.2. .sup.6 H.sub.3 PO.sub.3 also probably
present, but nmr not very sensitive for H.sub.3 PO.sub.3.
EXAMPLE 4
The cleavage reaction rate of a number of phosphonomethylamines
were determined and are tabulated in Table 3.
Table 3 ______________________________________ Cleavage Reaction
Rate ______________________________________ Reaction rate reported
in g-moles reacted/hr-gm of Norit "A" carbon catalyst at
115.degree. C and 100 psi O.sub.2 and approximately 0.1 molar in
tertiary amine (100 cc H.sub.2 O solvent). pH of Reaction Soln
Reaction Tertiary Amine at Start of Run.sup.3 Rate
______________________________________ N[CH.sub.2 PO(OH).sub.2
].sub.3 1.0 0.03-0.05 ##STR8## 1.5 0.009-0.011 ##STR9## 1.4
0.005-0.007.sup.2 CH.sub.3 N[CH.sub.2 PO(OH).sub.2 ].sub.2 0.9
0.003-0.004.sup.2 ______________________________________ .sup.1
Extrapolated from rate at 95.degree. C and 30 psi O.sub.2. .sup.2
Incomplete conversion of starting material. Reported reaction rate
extrapolated as well as possible from low conversion results.
.sup.3 pH at 95.degree. C (small pH change between 25.degree. C and
95.degree. C).
EXAMPLE 5
Oxidations of a triphosphonomethylamine were conducted in the
reactor described in Example 1, but with addition of sodium
hydroxide in some runs to determine the effect of base. Results are
reported in Table 4.
Table 4
__________________________________________________________________________
Effect of Base Addition on Reaction Rate and Product Distribution
__________________________________________________________________________
Solvent: 100 ml Water Cumulative pH Time Reaction Rate
Relative.sup.3 of Reaction Soln to end of % Time to that Without
Run Acid or Base Added At Start.sup.1 At End.sup.1 Run (min.)
Conv.sup.2 (min) Addition Remarks
__________________________________________________________________________
nitrilotrimethylenetriphosphonic acid, 10 grams, 0.5 g Norit "A"
Catalyst, 115.degree. C, 100 psi O.sub.2 R None 1. 1.2 200 60 50 1
Std run. 75 80 95-99 140 S 1.3 gms NaOH 1.5 1.9 180 65 50 .about.1
(1 Na/1 Reactant) 80 90 95 180 T 4.0 gms NaOH (3 Na/1 Reactant) 5.0
4.4 125 70 25 3 initially, Reaction appears to stop 85 55 however,
slows prior to complete con- 90 125 to <1. version Products (by
nmr): Besides the product, HN[CH.sub.2 PO(OH).sub.2 ].sub.2 and
fragments, HCOOH, and H.sub.3 PO.sub.3, a small quantity of an
unidentified compound was detected in each of the above runs. No
significant difference occurred in the amount of this compound with
base addition. The inter- mediate cleavage fragment, (HO).sub. 2
OPCHO, was identified in Run S.
__________________________________________________________________________
.sup.1 pH of (1) reactant tertiary amine (plus base if added) in
water an (2) product solution at end of run measured at 95.degree.
C. .sup.2 % conversion of tertiary amine as estimated by proton
nmr. .sup.3 Approximate.
The present process is useful in preparing secondary amines and it
is particularly notable that the reaction is generally very
selective to this reaction, producing little or no primary amine.
This is especially significant when the primary and secondary
amines are similar in properties, such as boiling point and the
like, and therefore difficult to separate by distillation or other
common procedures. It is also important that the oxidation reaction
can often conveniently be carried to high conversion to the desired
secondary amine, better than 80 or 90%, and that selectivity is
such that high yields are obtainable, often at least 80% or 90%
recovery of the desired secondary amine. It is also significant
that the oxidation can be conducted under relatively mild
conditions using a readily available oxidizing agent, oxygen,
available from air or other sources, and a material available in
ample commercial supply, activated carbon, as catalyst. In view of
its effectiveness, relatively low cost, and apparent resistance to
inactivation and suitability for recycling, the catalyst will
usually consist essentially of activated carbon. However, if
desired, the catalyst can comprise activated carbon and noble
metal.
* * * * *